There are several problems which are encountered when providing stimulation, such as neurostimulation, in the treatment of a disorder. One problem is that the stimulation field is not optimally focused within a target area, and stimulation occurs in adjacent areas. For example, providing low frequency stimulation to one area may assist in treatment of some types of disorders such as epilepsy, while this same stimulation causes side-effects by unintentionally stimulating adjacent areas. If the target tissue is distal from the electrode, the intervening tissue will usually be stimulated with the stimulation pattern which is intended for the target area. Providing certain types of stimulation to treatment areas, while supplying different types of stimulation to non-target areas, can decrease the occurrence of side-effects and enable improved treatment. Other problems which arise when electrically stimulating tissue are related to the transfer of energy from the electrical contact to the immediately adjacent tissue as well as through tissue itself. While certain types of stimulus waveforms may be good for treatment, these may be less well suited for transmitting energy from the electrodes to tissue, and subsequently through tissue itself. One approach to optimizing the desired effects of stimulation is to construct a “carrier wave” comprised of an oscillating carrier such as a train of high frequency pulses at some high frequency, f(H), which is modulated by some lower frequency mf(L) or contour mc(L). The contour itself may be an arbitrary waveform, a sine wave, an envelope derived from sensed activity, or a ramp of a specified rate of change of amplitude. This approach may be improved by changing the carrier frequency f(H) or by changing the modulating contour or its frequency at specified or random intervals, in order to increase entrainment and avoid habituation or adaptation to the stimulation. Another solution is to use signals which have desired characteristics for stimulation of, or transmission through, tissue which is not the target tissue, and which combine to create a vector field which stimulates target tissue in a desired manner. While methods of combining stimulation signals to produce desired vector fields have been used for dermal stimulation, and stimulation of other tissue, the methods described here are novel from, and offer advantages over, those of the prior art.